Proposals have been made for providing vehicles with retractable windshield wiper installations such that the wiper mechanism is parked in a closed housing below the hood of the vehicle, when the windshield wiper is out of use. When it is required for use, a motorised deployment mechanism is actuated so as to move the blade carrier out of the housing, and to put the various components of the installation into an appropriate position for wiping the glass of the vehicle.
In order to provide a system of this kind, it is necessary in particular to overcome the problem of how to fold the support for the wiper blade. In practice the wiper blade itself is carried by a blade carrier which is articulated to a blade carrier support, and the length of the latter and the blade carrier, taken together, is too large to enable it to be easily parked without the blade carrier being first folded back. Systems have already been proposed in which the blade carrier, articulated to the end of a blade carrier support arm, may be either folded back along this arm or deployed so as to form effectively an extension of the arm. A deployment motor, which is actuated at the instant when deployment or folding is required, causes the blade carrier to move from its folded position to its deployed position and vice versa. When the glass of the vehicle is to be wiped by the blade, the blade carrier is in its deployed position, and a wiper motor drives the arm and blade carrier together in an oscillating rotating movement, first in one direction and then in the other.
It happens that the wiper motor must drive, in rotational movement, an assembly the inertia of which is substantially greater than would be the case in non-retractable windshield wipers of the conventional type, because of the numerous additional components which are made necessary by the deployment and folding mechanism. In an oscillating wiper system in which it is necessary periodically to reverse the direction of rotation of the assembly, the inertia of the driven assembly is a very major factor to be taken into account.